pub async fn device shell(adb: &AdbExecutor, cmd: &str) -> Result<String> {
  // Normalize whitespace for blocklist check
  let normalized: String = cmd.split whitespace().collect::<Vec< >>().join(" ");
  let lower = normalized.to lowercase();

  let blocked = [
    "rm -rf",
    "rm -r",
    "reboot",
    "factory reset",
    "wipe",
    "format",
    "dd if=",
    "mkfs",
    "flash",
    "fastboot",
  ];
  for pattern in &blocked {
    if lower.contains(pattern) {
      return Err(ZeptoError::Tool(format!(
        "Blocked dangerous command containing '{}'",
        pattern
      )));
    }
  }